There is an old Kung Fu movie where a mother trained her two sons to beat an old Kung Fu Master. The father was killed by the master. The mother trained her two sons on her own. I remember in particular how the mother trained one of the boys to be invincible. She scolded his entire body in a tub of hot water and had the brother use a whip on him immediately afterwards. Most of the movie was the two training and getting stronger. The ended up defeating the Master in the end. I cannot remember the name of this movie. It was as good as The Executioners of Shaolin.